1. Field of the Invention
The present invention relates to a head-protecting airbag device whose airbag is mountable on an upper periphery of a window of a vehicle at an inboard side of the window in a folded-up configuration with an upper edge thereof secured to a vehicle body structure and is deployable downward over the window when fed with an inflation gas. Particularly, the invention relates to a head-protecting airbag device that operates adequately in the event of an oblique crash where an impact force acts on a vehicle obliquely either from the front or rear.
2. Description of Related Art
JP2012-96780 discloses a known head-protecting airbag device. The airbag of the airbag device is mounted on a vehicle body structure at an upper edge thereof. The airbag includes a bag body for covering an inboard side of a window, a tension belt which extends from a front end region of the bag body and fixed at the leading end to the peripheral edge of the window, and a position holding section which is a sheet in shape and covers an inboard side of the front end region of the bag body. In this conventional head-protecting airbag device, the bag body includes a terminal inflatable portion which is located at the front end of the bag body at deployment, a central inflatable portion which is located at the rear of and adjacent to the terminal inflatable portion, and a partitioning portion which partitions the terminal inflatable portion and central inflatable portion. The front end of the position holding section is connected to the front edge of the terminal inflatable portion and the rear end of the position holding section is connected to the rear edge of the central inflatable portion, thus the position holding section extends across the terminal inflatable portion and central inflatable portion. The root section of the tension belt is jointed to the partitioning portion partitioning the terminal inflatable portion and central inflatable portion, and the tension belt extends forward on an outboard side of the terminal inflatable portion. The width of the position holding section in a front and rear direction is smaller than that of the terminal inflatable portion and central inflatable portion in a condition where the bag body is inflated by itself.
When the airbag of the conventional head-protecting airbag device is deployed, the position holding section is deployed over the inboard side of the terminal inflatable portion and central inflatable portion while the tension belt extends forward from the partitioning portion which partitions the terminal inflatable portion and central inflatable portion. That is, since the position holding section has a short width, it is tensed on the inboard side of the bag body at airbag deployment, thus is capable of protecting a head of a vehicle occupant by its entire area despite of an existence of the partitioning portion between the terminal inflatable portion and central inflatable portion. Further, with the tension generated in the position holding section in a front and rear direction, the front end of the terminal inflatable portion is pulled toward an interior of a vehicle. The tension belt also pushes the terminal inflatable portion toward a vehicle interior such that the terminal inflatable portion is disposed farther inside of a vehicle interior than the central inflatable portion at airbag deployment with a tension generated in a front and rear direction.
That is, the conventional head-protecting airbag device uses the tensions of the tension belt and position holding section in order to deploy the terminal inflatable portion toward a vehicle interior. Although the position holding section pulls the front end of the terminal inflatable portion as well as the central inflatable portion by its tension, the tension belt pushes the terminal inflatable portion toward a vehicle interior but not the central inflatable portion since the tension belt extends from the partitioning portion between the terminal inflatable portion and central inflatable portion. Therefore, an improvement has been expected in order to deploy the central inflatable portion toward a vehicle interior as well.